body{
    background-color: silver;
}

div{
    overflow: hidden;
}


.cl{
    clear: both;
}

.wrapper{
    width: 98%;
    background-color: yellow;
    margin: 0 auto;  /* 水平居中 */
}

.header {
    width: 100%;
    background-color: thistle;
    margin: 0 auto;
    min-height: 200px;
}

.main{
    width: 100%;
    background-color: whitesmoke;
    margin: 0 auto;

}

.footer{
    width: 100%;
    background-color: rgb(145, 245, 178);
    margin: 0 auto;
    min-height: 200px;
}

.sidebar{
    float: left;
    width: 189px;
    min-height: 600px;
    background-color: tomato;
    padding-left: 10px;
    border-right: 1px dashed #fff222;
}

.right-side{
    float: right;
    width: 189px;
    min-height: 600px;
    background-color: rgb(163, 247, 219);
    padding-left: 10px;
    border-left: 1px dashed #fff222;
}

.content{
    /* float: left; */
    width: auto;
    min-height: 600px;
    background-color: turquoise;
    margin: 0 205px;    /* sidebar  200px  +  设计2个div间的间距5px */
}